Metal cap for electric incandescent lamps and its manufacture



April 5 1927.

L. P, GRANER METAL CAP FOR ELECTRIC INCANDESCENT LAMPS AND ITS MANUFACTURE Original Filed Nov. 17, 1923 fi vw m m er TA a m P H w. a w y b Patented Apr. 5, 1927..

UNITED STATES 1,623,836 PATENT OFFICE."

LADISLAUS rn'rna GRANER, or NEW YORK, r0 ennnmnntnc'rmc commnr,

METAL Original application filed N. Y., ASSIGNOR, BY MESNE ASSIGNMENTS, A CORPORATION OF NEW YORK.

CAP FOB ELECTBIQ INCANDESCENT LAMPS AND ITS MANUFACTURE.

November 17, 1923, Serial No. 675,400, and in the Netherlands January 1, 1923.

Divided and this application filed November 3, 1924. Serial No. 747,446.

is a. division of The resent application my application filed November Serial No. 675,400. g This invention relates to ,an. improved metal cap for electric lamps and the like, such for example as electric glow lamps, glow-discharge lamps, vapor lamps, discharge tubes and heating lamps.

When using metal caps for electric lamps and the like, the drawback is experienced that the cap extends beyond the lamp holder so that it is possible to touch parts of the cap under tension.

In order to obviate this disadvantage it has been proposed to provide the lamp holder with an insulating ring or envelope which will wholly protect the protruding part of the cap. Also caps of insulating material have already been manufactured.

It is an object of the invention to enable the usual type of lam holders to he used. Therefore that part 0 the metal cap adj acent the lamp is surrounded by a metal ring, which is insulated with regard to-the cap. It will be evident therefore that the metal ring always remains dead and being mounted on the art of the cap that extends beyond. the amp holder when the cap is screwed in, the risk of touching parts under tension is considerably reduced or altogther eliminated.-

According'to the invention the ring is fixed to the cap preferably by insulating material that at the same timeserves as a cement. I

As in insulating material one. of the well known phenol condensation products may be used or paper may be saturated with it. It may be easily applied in a thin layer and after hardening it is preferably adapted to rigidly unite the ring and the cap. One form of the product has the advantage that, once hardened, it does not melt at the temperature necessary for cementing the cap to the lamp whilst its insulating capacity does not decrease at a higher temperature.

One form of this product isan artificial resin that is everywhere on the market and it is produced by condensation of formaldehyde and phenol. It exists in three forms which are called A, B and C, and which by heat are transformed from one to the other when starting with the form A. 7

At ordinary temperatures one form of drawing represents a cap according to one.

embodiment of the invention.

By way of example, the accompanying drawing represents a lamp with a cap accordingto one form of the invention. As indicated, the cap 1, which is provided with themetal ring 3, is cemented to the electric lamp 2. As shown, the cap 1 and the ring 3 are separated from each other by the layer 6 of insulating or cement material of the kind mentioned.

In the drawing a lamp holder 4 of ordinary construction is shown in dotted lines. This holder, it will be seen, is provided with a ring 5 of insulating material. lVhen this holder is used in connection with a lamp embodying the features of the invention, such for example. as the lamp '2, it is im-i possible to. touch any metal part of cap owing ring 3.

The'cap may bemanufactured in a very simple manner, especially if the part that is to be insulated by the ring, is cylindrical.

The process of manufacturing the im proved caps according to the invention. is as follows:

The part to be insulated is coated with a.

layer of the insulating medium in a liquid or in a dissolved state, said insulating medium, after being dried, serving as a cement, such for example as shellac. When the insulating medium isdry the metal ring is applied after being-suitably heated or the dried insulating medium may first be coated afresh with a layer of the insulating medium in a liquid or in a dissolved state, so as to make the ring adhere to the insulating medium. The ring may be applied to the cap prior or subsequent to cementing the cap to the lamp, but preferably this operation is performed prior to the cementing.

to the protection afforded by the Another process according to the invention which is particularly advantageous is the following:

The part of the cap that is to be insulated is coated with a layer of a er that has been immersed in the liquid ibrm of a phenol condensation product .or in a solution of the A form. After the layer is driedits surface may be moistened afresh with the liquid A formor with a solution of the A form. Then a metal ring is forced around the layer while it is still moist and the as sembly dried and the A form of the produ'rt transformed by heat into the product.

The solution of the A form may for ex ample bean alcohol solution and the drying may be performed in a vacuum.

The transformation of the product may be preferably performed by gradually raising the temperature. 'At about 300 C. the form A is wholly transformed into the 'form C;

The application of the process according to the invention ensures a rigid attachment of the metal ring to the cap and at the same time good insulation. When having a thickness of about mm. the insulating layer may easily resist a voltage of 500 volts.

The invention may also be applied to advantage to caps in which a condenser is mounted. As a rule such caps have somewhat larger dimensions than the normal ones so that they further extend beyond the hold- C form of the ers andthe, risk at touching-the caps amde'r tension .is greater.

What I claim as new and desire to secure by Letters Patent of the United States, is 1. Theprocess of ap'plyin a metal ring to the outside cap terminal 0 an electric de-- .-vice having .a-sealed;enveiope which consists in coating the part of the cap over which the ring is to be applied with a layer of an insulating medium,- heating the ring and pressing it in place over the layer ofinsulation. v

. 2... The process of applying "a metal ring to the outside cap terminal of an electric device having a sealed envelope which consists in coatingthe part of the cap over which the ring is to be applied-with a layer of insulating material, applying the ring in place over the insulating material and heating thelayer to harden the material and seal the ring to the cap.

3. An electric device comprising a container with a terminalccap, an insulating ring about the base of the cap and a pro-'- tecting metal ring over the insulating ring serving to shield the cap when the device is in a socket and to avoid the cap being" exposed when sub ected to electric tension, said cap being cemented to the container and said ring being cemented to the cap.

In witness whereof, I have hereunto set my hand this 30th day ,of October, 1924.

LADISLAUS PETER GRANER. 

